The invention relates to bonding a thermoplastic elastomer to a magnesium based metal. More specifically, the invention relates to a thermoplastic elastomer strongly bonded to a magnesium containing metal using a specifically defined adhesive.
Bonding organic materials such as rubbers and plastics to metals is of great importance. Numerous articles provide a litany of mechanisms and solutions for bonding these distinct materials, with varying degrees of success. This is because different organic materials and metals have unique properties and varying degrees of compatibility.
For example, some organic materials have low energy surfaces while other organic materials have high energy surfaces. Some organic materials have plastic properties while other organic materials have elastomeric properties. Some organic materials have good heat resistance while other organic materials have poor heat resistance. Some organic materials have a high melt index while other organic materials have a low melt index. Organic materials may have different atoms which affect bonding properties, such as nitrogen containing materials, oxygen containing materials, silicon containing materials, halogen containing materials, sulfur containing materials, and so on.
Metals and metal alloys (collectively termed metals) possess varying characteristics. Metals vary in hardness/softness, corrosion resistance, toughness, wear resistance, resistance to chemical attack, tensile strength, types of oxides formed, and so on. With specific regard to magnesium, it is much more reactive than many other metals. Magnesium has a high sensitivity to salts such as chlorides. Magnesium also easily and quickly oxidizes. Magnesium oxide, formed by oxidation on a magnesium surface, is a very difficult surface on which to form a strong bond with other materials. Extreme care must be exercised with magnesium as fire and explosion hazards are associated with magnesium dust.
There are seemingly endless permutations of organic materials, and metals, all of which inherently have varying characteristics and properties. Improved bonding between specific types of organic materials and metals is therefore desired.
Furthermore, bonding organic materials to metals typically involves initially contacting the metal surface with a primer prior to joining the organic material with the metal. The primer serves improve adhesion between an adhesive and the metal. The primer, which strongly bonds with the adhesive, more strongly bonds to the metal than the adhesive. However, the use of a primer is not only time consuming, but also expensive. The use of additional chemicals such as primers and associated solvents presents disposal concerns and toxicity concerns. Bonding organic materials to metals without the need of a primer is therefore also desired.
Products made of an organic material bonded to a metal are used in many environments. Many of these products are used in harsh manufacturing environments. Manufacturing environments involve drastic and sudden changes in temperature and humidity, shock resistance (for example, to absorb the shock of a drop on concrete from a height of four feet), the ability to absorb vibrational movement, and resistance to petroleum based products, water-based cutting fluids, and industrial chemicals and solvents. There is a desire for products having organic materials to metals that maintain their integrity over time even in a manufacturing environment.
In one embodiment, the present invention relates to a bonded assembly made of a magnesium containing metal comprising at least about 25% by weight magnesium, a thermoplastic elastomer, and an adhesive between the magnesium containing metal and the thermoplastic elastomer, the adhesive comprising from about 20% to about 99% by weight of a polymeric material.
In another embodiment, the present invention relates to a bonded assembly made of a magnesium containing metal comprising from about 50% to about 99% by weight of magnesium and from about 1% to about 50% by weight of a non-magnesium metal, an olefinic thermoplastic elastomer, and an adhesive between the magnesium containing metal and the thermoplastic elastomer, the adhesive comprising from about 20% to about 99% by weight of at least one polymeric material and from about 1% to about 80% by weight of at least one polymeric complimentary material.
In yet another embodiment, the present invention relates to an apparatus made of a magnesium containing metal comprising from about 50% to about 99% by weight of magnesium and from about 1% to about 50% by weight of a non-magnesium metal, a chlorinated olefinic thermoplastic elastomer, and a heat activated solvent based adhesive between the magnesium containing metal and the thermoplastic elastomer, the adhesive comprising from about 20% to about 99% by weight of a halogenated polyolefin and from about 1% to about 80% by weight of at least one polymeric complimentary material.
In still yet another embodiment, the present invention relates to a method of making a bonded assembly involving applying an adhesive to at least a portion of a magnesium containing metal to provide an adhesive coated metal, the adhesive comprising from about 20% to about 99% by weight of a polymeric material and the magnesium containing metal comprising at least about 25% by weight magnesium, and contacting the adhesive coated metal with a thermoplastic elastomer under sufficient pressure for a sufficient period of time to bond the thermoplastic elastomer to the adhesive coated metal.